Integrity Challenges and Countermeasures of the Offshore CCUS Based on CO₂-EOR

CO₂ can be used to improve the recovery efficiency of offshore oil and gas fields. Not only does it increase the utilization rate of oil and gas resources but it also helps capture and store regional CO₂. The long-term safety of offshore oil and gas wells is a key factor for carbon capture, utilization, and storage(CCUS), but corresponding theories and technologies need to be improved. By analyzing and summarizing key technologies of CCUS wellbore integrity in offshore oil and gas fields both in China and abroad, the technical challenges that restrict CCUS wellbore integrity in shallow offshore oil fields were analyzed. The studies covered cementing of carbon sequestration wells, research and prevention of carbon sequestration casing corrosion, carbon sequestration wellbore plugging caused by water-rock reaction, wellbore environment monitoring and diagnosis, and other technologies. In addition, the development prospect of CCUS in shallow offshore oil and gas fields was predicted in consideration of the national target of carbon peaking and carbon neutrality goals, enhanced oil recovery(EOR)/enhanced gas recovery(EGR) technology requirements, and experience of new domestic and foreign technologies. Although China is preliminarily capable of carrying out offshore CCUS, technology research should be strengthened in the aspects of high-strength CO₂ corrosion-resistant cement slurry systems, low-cost anticorrosive material selections, high-efficient wellbore descaling and plugging processes, CO₂ leakage monitoring technology, and three-dimensional stress field research of underground traps, so as to improve its CCUS application level.